i2c slave with PMS150C

i2c_stm.c

#define I2C_SLAVE_ADDRESS (0xA0 >> 1)
#define BUF_SIZE 16

enum {
    IDLE,
    START,
    STOP,
    ADDR,
    OP,
    READDATA,
    WRITEDATA,
    IACK1,
    IACK2,
    WACK1,
    WACK2,
    RACK
};

enum {
    LOW,
    HIGH
};

enum {
    INPUT,
    OUTPUT
};

sda	equ PA.4;
scl	equ PA.3;
sdac    equ PAC.4;
sclc    equ PAC.3;

BYTE last, current;
BYTE sda_change, scl_change;

BYTE state;
BYTE data;
BYTE len;
BYTE buf[BUF_SIZE];
WORD ptr;
BYTE wrt;
BYTE pause_sda;

void clear_sda()
{
    pause_sda = 1;
    sdac = OUTPUT;
    sda = LOW;
}

void release_sda()
{
    pause_sda = 0;
    sdac = INPUT;
    sda = HIGH;
}

void sda_low()
{
    pause_sda = 1;
    sdac = OUTPUT;
    sda = LOW;    
}

void sda_high()
{
    pause_sda = 1;
    sdac = INPUT;
    sda = HIGH;    
}

void check_scl()
{
    if (scl == HIGH) {
        switch(state) {
            case ADDR:
                if (sda)
                    data = (data << 1) | 1;
                else
                    data = (data << 1);
                
                len++;
                
                if (len < 7)
                    break;
                
                if (data != I2C_SLAVE_ADDRESS)
                    state = IDLE;
                else
                    state = OP;
            break;
            case OP:
                //读完7位地址位，剩1位读写位
                if (sda)
                    data = 1;
                else
                    data = 0;
                
                state = IACK1;
            break;
            case IACK1:
                state = IACK2;
            break;
            case WRITEDATA:
                if (sda)
                    data = (data << 1) | 1;
                else
                    data = (data << 1);
                
                len++;
                
                if (len < 8)
                    break;
                
                len = 0;

                *ptr = data;
		ptr++;

                data = 0;
                state = WACK1;
            break;
            case WACK1:
                state = WACK2;
            break;
            case READDATA:
                if (len < 8)
                    break;
                
                ptr++;
		data = *ptr;
                len = 0;
                state = RACK;
            break;
            case RACK:
                if (sda == HIGH)
                    state = IDLE;
                else
                    state = READDATA;
            break;
            default:
            break;
        }
    } else {
        switch(state) {
            case IACK1:
                clear_sda();
            break;
            case IACK2:
                release_sda();
                
                if (data == 0) {
                    len = 0;
                    ptr = buf;
                    state = WRITEDATA;
                    wrt = 1;
                } else {
                    state = READDATA;
                    wrt = 0;
                    ptr = buf; ptr++; //指向data0
                    
                    len = 1;
                    //make sda high/low

                    data = *ptr;
                    if (data.7) {
                        sda_high();
                    } else {
                        sda_low();
                    }
		    data <<= 1;
                }
            break;
            case WACK1:
                clear_sda();
            break;
            case WACK2:
                release_sda();
                state = WRITEDATA;
            break;
            case READDATA:
                //make sda high low
                if (data.7) {
                    sda_high();
                } else {
                    sda_low();
                }
		data <<= 1;
                len++;
            break;
            case RACK:
                release_sda();
            break;
            default:
            break;
        }
    }
}

void check_sda()
{
    //pms150c主动操作sda的时候，不检查sda是否跳变
    if (pause_sda)
        return;
    
    if (scl == HIGH && !scl_change) {
        if (sda == HIGH) {
            //scl高电平，sda跳成高电平，是STOP信号
            state = IDLE;
            
            if (wrt) {
                //write done
            } else {
                //read done
            }
            
            len = 0;
            ptr = buf;
            data = 0;
        } else {
            //scl高电平，sda跳成高电平，是START信号
            //状态机转成准备接收地址的状态
            state = ADDR;
            len = 0;
            ptr = buf;
            data = 0;
        }
    }
}

void i2c_init()
{
	//设置所有pin为输入
	PAC = 0;

	//sda scl加上弱上拉
	PAPH = _FIELD(sda, scl);

	state = IDLE;
	data = 0;
	len = 0;
	ptr = buf;
	pause_sda = 0;

	current = PA;
	last = current;
}

void	FPPA0 (void)
{
	.ADJUST_IC	SYSCLK=IHRC/2, IHRC=16MHz, VDD=5V;
		//	WatchDog Disable, RAM 0 ~ 0xF temporary be used
	//	You can add the follow code :
	//		CLKMD.En_WatchDog	=	1;		// WatchDog Enable


	i2c_init();

	while (1)
	{
        	//读取
        	current = PA;
        	sda_change = (last ^ current) & _FIELD(sda);
        	scl_change = (last ^ current) & _FIELD(scl);
        	last = current;
        
        	if (scl_change)
            		check_scl();
        
        	if (sda_change)
            		check_sda();
	}
}